Gas turbines constructed as aircraft engines comprise at least one compressor, at least one combustion chamber and at least one turbine. Aircraft engines are known in the prior art which on the one hand comprise three compressors positioned upstream of the combustion chamber and three turbines positioned downstream of the combustion chamber. The three compressors comprise a low pressure compressor, a medium pressure compressor and a high pressure compressor. The three turbines comprise a high pressure turbine, a medium pressure turbine and a low pressure turbine. According to the prior art, the rotors of the high pressure compressor and of the high pressure turbine are connected with each other by a shaft. The medium pressure compressor rotor and the medium pressure turbine rotor are interconnected by a shaft. The low pressure compressor rotor and the low pressure turbine rotor are interconnected by a respective shaft. The three shafts concentrically enclose one another and are therefore nested within one another.
For example, if the shaft that interconnects the medium pressure compressor with the medium pressure turbine breaks, then the medium pressure compressor can no longer take-off work or power from the medium pressure turbine. As a result, an excessive rotational speed (racing) can occur at the medium pressure turbine. Such racing of the medium pressure turbine must be avoided because thereby the entire aircraft engine can be damaged. Thus, for safety reasons a shaft break in a gas turbine must be detectable with certainty in order to stop a fuel supply to the combustion chamber when a shaft break occurs. Such a detection of a shaft break makes difficulties particularly when the gas turbine as described above comprises three shafts arranged concentrically one within the other and thus nested one within the other. In this case particularly the detection of a shaft break of the intermediate shaft which couples the medium pressure turbine with the medium pressure compressor, makes difficulties.